1. Field of the Invention
The present invention relates to a light-alloy piston with a combustion bowl provided with fine-grain carbon armoring.
2. The Prior Art
It is known from U.S. Pat. No. 4,334,507 to provide pistons with combustion bowls where the edge of the bowl has armor of sintered, porous chrome-nickel steel. During manufacture of the piston, the porous chrome-nickel steel is infiltrated by the melt which is under pressure.
Furthermore, it is known from DE-PS 34 30 056 to provide the edge of the bowl with an armoring made of Al.sub.2 O.sub.3 fibers. The fibers are made into a fiber preform. The preform is infiltrated by the melt which is under pressure during manufacture of the piston.
The reason for adding armor is to prevent cracks frequently caused on the edge of the bowl due to stresses caused by temperature changes.
The drawback of infiltrating the Cr-Ni-steel armor with the basic Al-material of the piston is its poor workability, its higher specific weight, and its lower strength as compared to the ceramic-fiber composite material.
The Al.sub.2 O.sub.3 fibers also have drawbacks in that during manufacture and processing, the ceramic-fiber composite material is subject to stricter environmental protection requirements, and its disposal is difficult because the fibers and the melt cannot be separated from each other. Both processes have the common drawback that the melt has to be acted upon by pressure in order to completely fill the open pores of the armor with the melt.
Thus, the invention is based on providing an armor material for the edge of the bowl, which safely prevents cracking on the edge of the bowl, without having the aforementioned drawbacks.